marshmallow-sqlalchemy¶
Release v0.28.0 (Changelog)
SQLAlchemy integration with the marshmallow (de)serialization library.
Declare your models¶
import sqlalchemy as sa
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import scoped_session, sessionmaker, relationship, backref
engine = sa.create_engine("sqlite:///:memory:")
session = scoped_session(sessionmaker(bind=engine))
Base = declarative_base()
class Author(Base):
__tablename__ = "authors"
id = sa.Column(sa.Integer, primary_key=True)
name = sa.Column(sa.String, nullable=False)
def __repr__(self):
return "<Author(name={self.name!r})>".format(self=self)
class Book(Base):
__tablename__ = "books"
id = sa.Column(sa.Integer, primary_key=True)
title = sa.Column(sa.String)
author_id = sa.Column(sa.Integer, sa.ForeignKey("authors.id"))
author = relationship("Author", backref=backref("books"))
Base.metadata.create_all(engine)
Generate marshmallow schemas¶
from marshmallow_sqlalchemy import SQLAlchemySchema, auto_field
class AuthorSchema(SQLAlchemySchema):
class Meta:
model = Author
load_instance = True # Optional: deserialize to model instances
id = auto_field()
name = auto_field()
books = auto_field()
class BookSchema(SQLAlchemySchema):
class Meta:
model = Book
load_instance = True
id = auto_field()
title = auto_field()
author_id = auto_field()
You can automatically generate fields for a model’s columns using SQLAlchemyAutoSchema.
The following schema classes are equivalent to the above.
from marshmallow_sqlalchemy import SQLAlchemyAutoSchema
class AuthorSchema(SQLAlchemyAutoSchema):
class Meta:
model = Author
include_relationships = True
load_instance = True
class BookSchema(SQLAlchemyAutoSchema):
class Meta:
model = Book
include_fk = True
load_instance = True
Make sure to declare Models before instantiating Schemas. Otherwise sqlalchemy.orm.configure_mappers() will run too soon and fail.
Note
Any column_property on the model that does not derive directly from Column
(such as a mapped expression), will be detected and marked as dump_only.
hybrid_property is not automatically handled at all, and would need to be
explicitly declared as a field.
(De)serialize your data¶
author = Author(name="Chuck Paluhniuk")
author_schema = AuthorSchema()
book = Book(title="Fight Club", author=author)
session.add(author)
session.add(book)
session.commit()
dump_data = author_schema.dump(author)
print(dump_data)
# {'id': 1, 'name': 'Chuck Paluhniuk', 'books': [1]}
load_data = author_schema.load(dump_data, session=session)
print(load_data)
# <Author(name='Chuck Paluhniuk')>
Get it now¶
pip install -U marshmallow-sqlalchemy
Requires Python >= 3.7, marshmallow >= 3.0.0, and SQLAlchemy >= 1.3.0.
